Design and implementation of controllers in oil-field drill-string systems for rate-of-penetration increase

Oil-field drilling systems are known to exhibit self-excited vibrations, which decrease the performance of drilling systems and accelerate bit wear. In this project, we focus on controller design to eliminate torsional stick-slip vibrations of drill-string systems.

Drilling systems are used for the exploration and production of oil and gas, mineral resources and geo-thermal energy. Drilling systems are known to exhibit self-excited vibrations, which may lead to whirling, bit bouncing and (torsional) stick-slip. Due to these vibrations, the drilling efficiency decreases, wear of the drill bit accelerates and the drill-string may be damaged.

The first research line of this project opts to develop a controller that eliminates torsional stick-slip vibrations of the drill-string system. This is an important topic because current industrial controllers are not always able to eliminate stick-slip vibrations, due to increasing demands on the operating envelope and a tendency towards drilling deeper and inclined wells. Two main reasons are the influence of 1) multiple dynamical modes of the drill-string and 2) uncertainty in the bit-rock interaction law on stick-slip oscillations. Another challenging aspect is the lack of (real-time) downhole measurements available for feedback control.

The second research line focuses on the coupling between torsional and axial vibrations to exploit insight into this coupling to take passive and/or active measures to adapt the axial dynamics to suppress torsional vibrations.